Method and apparatus for testing liquid crystal display device

ABSTRACT

A method and apparatus for testing a liquid crystal display device are provided to detect a defect location precisely and rapidly without requiring a jig. The method includes providing a substrate to inspect, wherein the substrate includes signal wirings, drive switches and capacitors formed in an effective display area of the substrate; radiating a light onto an inspection switch device and thereby supplying an inspection voltage from an inspection line to one of the drive switches through the signal wirings, so as to charge one of the capacitors; and determining if there is a defect in the effective display area of the substrate by reading the charged voltage of the capacitor.

[0001] The present application claims, under 35 U.S.C. § 119, thepriority benefit of Korean Patent Application No. P2003-28644, filed May6, 2003, the entire contents of which are herein fully incorporated byreference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates in general to a liquid crystaldisplay (LCD) device and, more particularly, to a method and apparatusfor testing an LCD device to detect a defective location on the LCDdevice precisely and rapidly without requiring a jig.

[0004] 2. Description of the Related Art

[0005] Display apparatuses have become important as visual informationtransferring media. Among the display apparatuses, a cathode ray tube iswidely used at present, but is disadvantageous in that its weight andvolume are large. Therefore, various types of flat display apparatuseshave been developed that are capable of overcoming the defects of thecathode ray tube. An LCD, a field emission display (FED), a plasmadisplay panel (PDP), and an electroluminescence (EL) display aredifferent examples of flat display apparatus. Most of these apparatusesare available in the market.

[0006] The LCD device is easily adaptive due its smallness whichimproves productivity. Thus, it is quickly replacing the cathode raytubes in many applications. In particular, the LCD device of an activematrix type for driving a liquid crystal cell by using a thin filmtransistor (hereinafter referred to as “TFT”) has an advantage in thatthe picture quality it provides is excellent, and its power consumptionis low. Such LCDs have been rapidly developed into a large size and highdefinition due to the recent productivity technology and research.

[0007] As shown in FIG. 1, in the LCD of the active matrix type, a colorfilter substrate 22 and a TFT array substrate 23 are assembled with aliquid crystal layer 15 therebetween. The LCD shown in FIG. 1 representsa portion of a total effective display.

[0008] The color filter substrate 22 includes an upper glass substrate12, and a color filter 13 and a common electrode 14 formed thereon.Attached on a front surface of the upper glass substrate 12 is apolarization plate 11. In the color filter 13, the color filter layersof red, green and blue colors are disposed and transmit a light ofspecial wavelength bandwidth to display a color. A black matrix (notshown) is formed between the color filters 13 of the adjacent color.

[0009] Data lines 19 and gate lines 18 cross each other on the entiresurface of a lower glass substrate 16 in the TFT array substrate 23.TFTs 20 are formed at the intersections of the gate and data lines 18and 19. A pixel electrode 21 is formed at a cell region between each ofthe data lines 19 and gate lines 18 on the entire surface of the lowerglass substrate 16. Each TFT 20 switches a data transfer path betweenthe corresponding data line 19 and the corresponding pixel electrode 21in response to a scanning signal from the corresponding gate line 18 andthus drives the corresponding pixel electrode 21. A polarization plate17 is installed on a rear surface of the TFT array substrate 23.

[0010] The liquid crystal layer 15 adjusts a transmitting quantity of anincident light via the TFT array substrate 23 in response to an electricfield applied thereto. The polarization plates 11 and 17 installed onthe color filter substrate 22 and the TFT array substrate 23 transmitthe light polarized to one direction. When the liquid crystal layer 15is at 90°TN mode, the polarization directions of the polarization plates11 and 17 vertically cross each other. An alignment film (not shown) isformed on the facing surfaces of the color filter substrate 22 and theTFT array substrate 23.

[0011] A process for fabricating the LCD device of the active matrixtype is divided into a substrate cleaning, a substrate patterning, analignment forming/rubbing, a substrate assembling/a liquid crystalmaterial injecting, a mounting, an inspecting and a repairing.

[0012] Generally, impurities on the substrate surface of the LCD deviceare removed by a detergent in the substrate cleaning process. Thesubstrate patterning process is divided into a patterning process of thecolor filer substrate and a patterning process of the TFT arraysubstrate. The alignment film forming/rubbing process involves applyingan alignment film to each of the color filter substrate and the TFTarray substrate and rubbing the alignment film. The substrateassembling/liquid crystal injecting process is to assemble the colorfilter substrate and the TFT array substrate by using a sealant, toinject the liquid crystal and a spacer through a liquid crystalinjection hole and then to seal the liquid crystal injection hole.

[0013] In the mounting process of the liquid crystal panel, a tapecarrier package (hereinafter referred to as “TCP”) is connected to a padpart on the substrate, wherein the TCP has integrated circuits mountedthereon such as a gate drive integrated circuit and a data driveintegrated circuit. Such drive integrated circuits may be directlymounted on the substrate by using a chip on glass (hereinafter referredto as “COG”) method besides a TAB (Tape Automated Bonding) using the TCPdescribed above.

[0014] The inspecting process includes a first electrical inspectionperformed after forming a variety of signal wirings such as the dataline and the gate line on the TFT array substrate and the pixelelectrode, and a second electrical inspection and a visual inspectionperformed after the substrate assembly/liquid crystal injection process.Specifically, the electrical inspection of the signal wirings of the TFTarray substrate and the pixel electrode of the lower substrate performedbefore the substrate assembling process may reduce an undesirable ratioand a waste matter and may find a defective substrate capable ofrepairing at an early stage.

[0015] The repairing process performs a restoration for a repairablesubstrate determined by the inspecting process. However, in theinspecting process, defective substrates beyond repair are discarded.

[0016] The device as shown in FIG. 2 may be used in an inspectionprocess carried out before the substrate assembling. The inspectiondevice shown in FIG. 2 is fully described in U.S. Pat. No. 5,377,030.

[0017] Referring to FIG. 2, the inspection device of the related artincludes an inspection switch device 34 for selectively supplying avoltage from an inspection power supply 36 to a video signal inputwiring, and a voltage from a current-voltage amplifier 38 under thecontrol of a driving signal generation unit 35, a scanning switch device30 for supplying the inspection voltage from the video signal inputwiring 32 to the data lines 28 of a TFT array 46 of an active matrix LCDunder control of an H scanning circuit 24, a V scanning circuit 42 fordriving the gate lines 26 of the TFT array 46 under control of thedriving signal generation unit 35, and a determining unit 40 fordetermining an electrical defect in the TFT array 46. The data lines 28and gate lines 26 cross each other in the TFT array 46, and TFTs areformed at their intersections. Further, common wirings 33 and a storagecapacitor Cst between the common wirings 33 and a drain electrode of theTFT are formed in the TFT array 46.

[0018] The inspection of the TFT array 46 includes a sequence of loadinga substrate having the TFT array 46 formed thereon to the inspectiondevice, writing the inspection voltage to the TFT array 46 and reading asignal from the TFT array 46.

[0019] After loading the substrate having the TFT array 46 to theinspection device, the writing process of the inspection voltage isperformed. In the writing process of the inspection voltage, theinspection switch device 34 is connected to the first terminal 34 a andthe scanning switch device 30 is turned on under control of the Hscanning circuit 24. Accordingly, the inspection voltage generated fromthe inspection power supply 36 is supplied to the data lines 28 of theTFT array 46 via the inspection switch device 34, the video signal inputwiring 32 and the scanning switch device 30. At the same time, the Vscanning circuit 42 supplies a test scan voltage to the gate lines 26under control of the driving signal generation unit 35. Then the TFTsare turned on in the selected lines of the TFT array 46, and theinspection voltage on the data lines 28 is charged to the storagecapacitors Cst via the TFTs.

[0020] In the reading process of the inspection voltage, the inspectionswitch device 34 is connected to the second terminal 34 b and thescanning switch device 30 is turned on under control of the H scanningcircuit 24. At the same time, the V scanning circuit 42 supplies thetest scan voltage to the gate lines 26 under control of the drivingsignal generation unit 35. Then, the TFTs are turned on in the selectedlines of the TFT array and the voltage of the corresponding storagecapacitor Cst is supplied to the current-voltage amplifier 38 via theTFTs, the data line 28, the scanning switch device 30, the video signalinput wiring 32 and the inspection switch device 34. The voltage readfrom the storage capacitor Cst is supplied to the determining unit 40after being amplified by the current-voltage amplifier 38, and thedetermining unit 40 determines if there is a defect in the TFT array 46based on the voltage supplied by the current-voltage amplifier 38.

[0021] However, since the substrate (having the TFT array 46) to beinspected is not equipped with the driving circuit and the inspectiondevice, a separate jig is needed to accommodate the driving signalgeneration unit 35, the H scan circuit 24, the V scan circuit 42, thescanning switch device 30, the video signal input wiring 32, theinspection switch device 34, the inspection power supply 36, thecurrent-voltage amplifier 38 and the determining unit 40. As a result,there is a problem that the inspection device of the related art shownin FIG. 2 needs a high price jig. Further, if the resolution of the LCDor a model is changed, the jig needs to be changed correspondingly. Onthe other hand, if the TFT array 46 is inspected by a block dividingmethod concurrently driving a plurality of gate lines 26 and a pluralityof data lines 28, the number of input/output terminals of the jig andthe circuit price of the jig may be reduced. However, there is anotherproblem that a defect location within the block cannot be detected withprecision.

SUMMARY OF THE INVENTION

[0022] Accordingly, it is an object of the present invention to providea method and apparatus for testing an LCD display device which candetect a defective location precisely and rapidly without requiring ajig.

[0023] It is another object of the present invention to provide a methodand apparatus for testing an LCD which overcomes the limitations andproblems of the related art.

[0024] In accordance with an aspect of the invention, a method ofinspecting a liquid crystal display device using an inspectionapparatus, the inspection apparatus including a light source, at leastone inspection line and at least one inspection switch device connectedto the inspection line, the method includes: providing a substrate,wherein the substrate includes a plurality of signal wirings, aplurality of drive switches, and a plurality of capacitors formed in aneffective display area of the substrate; radiating a light generatedfrom the light source of the inspection apparatus onto the at least oneinspection switch device and thereby supplying an inspection voltagefrom the at least one inspection line to a corresponding one of thedrive switches through the signal wirings, so as to charge acorresponding one of the capacitors; and determining if there is adefect in the effective display area of the substrate by reading thecharged voltage of the corresponding one of the capacitors.

[0025] In accordance with an aspect of the invention, a method ofinspecting a substrate device, the substrate device including signalwirings, drive switches and capacitors formed in a main area of thesubstrate device, and an inspection line and an inspection switch formedat an exterior of the main area, the drive switches being coupled to thecapacitors, the inspection switch being coupled to the inspection line,the method includes: supplying an inspection voltage to the inspectionline of the substrate device; charging one of the capacitors with theinspection voltage through the signal wirings; and determining if thereis a defect in the substrate device by reading the charged voltage ofthe capacitor.

[0026] In accordance with an aspect of the invention, a method ofinspecting a display part of a liquid crystal display device, the methodincludes: providing an inspection apparatus as a removable portion ofthe liquid crystal display device; inspecting the display part of theliquid crystal display device using the inspection apparatus; removingthe inspection apparatus from the liquid crystal display device afterthe inspection is completed; and attaching driving circuits to theliquid crystal display device having the inspection apparatus removedtherefrom.

[0027] In accordance with an aspect of the invention, a method ofinspecting a display part of a liquid crystal display device, the methodincludes: providing an inspection apparatus as an integral part of theliquid crystal display device; inspecting the display part of the liquidcrystal display device using the inspection apparatus; covering theinspection apparatus with a light cut-off layer after the inspection iscompleted; and attaching driving circuits to the liquid crystal displaydevice after the inspection is completed.

[0028] In accordance with an aspect of the invention, an inspectionapparatus for a liquid crystal display device, the liquid crystal deviceincluding a plurality of signal wirings, a plurality of driving switchdevices and a plurality of capacitors formed on a substrate and formedin an effective display area of the liquid crystal display device, theapparatus includes: at least one inspection line formed at an exteriorof the effective display area of the liquid crystal display device; atleast one inspection switch device connected to the at least oneinspection line and formed at an exterior of the effective display area;a light source to radiate light onto the at least one inspection switchdevice, so as to turn on the at least one inspection switch device andto charge an inspection voltage from the at least one inspection lineonto one of the capacitors; and a control part to read the chargedvoltage of the one of the capacitors and thereby determine if there is adefect in the effective display area of the liquid crystal displaydevice.

[0029] In accordance with an aspect of the invention, an apparatus forinspecting a substrate of a liquid crystal display device, the substrateincluding a plurality of signal wirings, a plurality of drive switchesand a plurality of capacitors formed in an effective display area of thesubstrate, the apparatus includes: a light source to radiate light; atleast one inspection line formed at an exterior of the effective displayarea of the substrate; at least one inspection switch device connectedto the at least one inspection line and formed at an exterior of theeffective display area of the substrate, wherein the at least oneinspection switch device is radiated with the light from the lightsource so as to be turned on to supply an inspection voltage of the atleast one inspection line to a corresponding one of the drive switches,whereby a corresponding one of the capacitors is charged through thesignal wirings; and a determining part to determine if there is a defectin the effective display area of the substrate by reading the chargedvoltage of the corresponding one of the capacitors.

[0030] In accordance with an aspect of the invention, a display part ofa liquid crystal display device, includes: a substrate; a displaycircuit on the substrate for performing a display function of the liquidcrystal display device; and an inspection apparatus formed at anexterior of the display circuit and being a removable portion of theliquid crystal display device, wherein after the display circuit isinspected for any defect using the inspection apparatus, the inspectionapparatus is removed from the liquid crystal display device.

[0031] In accordance with an aspect of the invention, a display part ofa liquid crystal display device, includes: a substrate; a displaycircuit on the substrate for performing a display function of the liquidcrystal display device; an inspection apparatus formed as an integralpart of the liquid crystal display device at an exterior of the displaycircuit; and a light cut-off layer covering the inspection apparatusafter the display circuit is inspected using the inspection apparatus;and driving circuits attached to the liquid crystal display device afterthe display circuit is inspected using the inspection apparatus.

[0032] These and other objects of the present application will becomemore readily apparent from the detailed description given hereinafter.However, it should be understood that the detailed description andspecific examples, while indicating preferred embodiments of theinvention, are given by way of illustration only, since various changesand modifications within the spirit and scope of the invention willbecome apparent to those skilled in the art from this detaileddescription.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] These and other objects of the invention will be apparent fromthe following detailed description of the embodiments of the presentinvention with reference to the accompanying drawings, in which:

[0034]FIG. 1 is a perspective view illustrating a liquid crystal displaydevice of an active matrix type of the related art;

[0035]FIG. 2 is a circuit diagram illustrating an inspection device ofthe related art for inspecting a liquid crystal display device;

[0036]FIG. 3 is a block diagram illustrating an inspection device of aliquid crystal display device according to an embodiment of the presentinvention;

[0037]FIG. 4 illustrates a substrate of a liquid crystal display deviceaccording to an embodiment of the present invention;

[0038]FIG. 5 is a diagram for explaining a writing process of aninspection voltage with respect to an inspection method of a liquidcrystal display device according to an embodiment of the presentinvention;

[0039]FIG. 6 is a diagram for explaining a reading process of a storagecapacitor voltage with respect to an inspection method of a liquidcrystal display device according to an embodiment of the presentinvention;

[0040]FIG. 7 illustrates a state that a data driving circuit and agate/scan driving circuit are installed on a substrate of a liquidcrystal display device after an edge of the substrate is removed along acutting line 400 shown in FIG. 4 according to an embodiment of thepresent invention; and

[0041]FIG. 8 illustrates a state that an inspection circuit shown inFIG. 4 is shielded with a light cutting-off layer, and a data drivingcircuit and a gate driving circuit are installed on a substrate of aliquid crystal display device according to another embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0042] Reference will now be made in detail to the preferred embodimentsof the present invention, examples of which are illustrated in theaccompanying drawings.

[0043] Hereinafter, as referring to FIGS. 3 to 8, the preferredembodiments of the present invention will be explained in full detail.

[0044] Referring to FIG. 3, an inspection device for a liquid crystaldisplay according to a preferred embodiment of the present inventionincludes a light source 1 for radiating a light 1 a on a substrate 8 tobe inspected, a writing and reading circuit 6, a voltage source 7 forsupplying an inspection voltage to the writing and reading circuit 6, alight source driving circuit 2 for driving the light source 1, a displaydevice 4, and a controlling and determining circuit 3 for controlling auser interface device 5. All the components of the inspection device areoperatively coupled. The substrate 8 includes a TFT array formed thereonand is part of a liquid crystal display device.

[0045] The light source 1 is driven by a power from the light sourcedriving circuit 2 to generate the light 1 a which will then be focusedon the substrate 8 to be inspected.

[0046] The writing and reading circuit 6 supplies the inspection voltagefrom the voltage source 7 (or some other source) to an inspectionterminal of the substrate 8 under control of the controlling anddetermining circuit 3, and reads the voltage generated in the substrate8 in response to the inspection voltage. The writing and reading circuit6 supplies the read voltage to the controlling and determining circuit3.

[0047] The controlling and determining circuit 3 controls the lightsource driving circuit 2 to turn on or off the light source 1 andcontrols the writing and reading circuit 6. Further, the controlling anddetermining circuit 3 compares the read voltage from the writing andreading circuit 6 with a predetermined reference voltage and determinesa badness/defectiveness of the substrate 8 being inspected in accordancewith the comparison result. Then the controlling and determining circuit3 generates determination result data and supplies the determinationresult data to the display device 4 so that the determination result canbe displayed to a user or an inspection operator. This allows the useror inspection operator to recognize the defectiveness of the substrate 8in real time. The user or inspection operator can issue a command orinstruction to process the defective substrate via the user interface 5such as a keyboard, a mouse, etc.

[0048] The controlling and determining circuit 3 can include a ROM (orother memory) having the predetermined reference data voltages storedtherein in a lookup table or some other format, so that the referencevoltages can be accessed and used to compare with the read voltage. Thecontrolling and determining circuit 3 can include an operation devicefor performing the detect determination test for the substrate. Theoperation device may be implemented with one or more computer programsembodied on a computer-readable medium such as ROM, optical disc, etc.

[0049] Further, the inspection device according to the embodiment of thepresent invention includes a stage for moving the substrate 8 to beinspected and/or a unit for moving the light source 1 such as anactuator.

[0050]FIG. 4 illustrates an example of a TFT array substrate of a liquidcrystal device according to the embodiment of the present invention. Forinstance, the substrate 8 in FIG. 3 can be the substrate having thestructure shown in FIG. 4.

[0051] Referring to FIG. 4, the TFT array substrate according to thepresent invention includes data lines DL1 to DLm and gate lines DGL andGL1 to GLn crossing mutually, TFTs formed at the intersections of thedata lines DL1 to DLm and the gate lines DGL and Gl1 to GLn, a storagecapacitor Cst connected to each of the TFTs, an electrostatic damageprotection line 404 crossing with the data lines DL1 to DLm and the gatelines DGL and GL1 to GLn, electrostatic damage protection devices 403 aand 403 c connected between the electrostatic damage protection line 404and the data lines DL1 to DLm, and electrostatic damage protectiondevices 403 b and 403 d connected between the electrostatic damageprotection line 404 and the gate lines DGL and GL1 to GLn. Thesecomponents are all operatively coupled.

[0052] An inspecting voltage is applied selectively or simultaneously tothe data lines DL1 to DLm during the inspecting process, whereas thevideo data is supplied to the data lines DL1 to DLm upon a normaldriving.

[0053] The gate lines DGL and GL1 to GLn include an uppermost dummy gateline DGL not connected to the TFTs and the gate lines GL1 to GLnconnected to the TFTs. The gate lines DGL and GL1 to GLn supply theinspection voltage to the TFTs during the inspection process to select aline having the inspection voltage supplied thereto, and supply thedriving scan voltage to the TFTs to select the line having the videodata voltage supplied thereto upon a normal driving.

[0054] The gate electrodes of the TFTs are connected to the gate linesGL1 to GLn and the source electrodes of the TFTs are connected to thedata lines DL1 to DLm. The drain electrodes of the TFTs are connected tothe storage capacitors Cst. Each TFT is turned on when the scan voltagehigher than the threshold voltage of the corresponding TFT is suppliedto the corresponding one of the gate lines GL1 to GLn, which in turnsupplies the voltage on the corresponding one of the data lines Dl1 toDLm to the corresponding storage capacitor Cst.

[0055] For each TFT, the storage capacitor Cst is formed between thedrain electrode of the TFT and the prestage gate line or is formedbetween the drain electrode of the TFT and a separate common electrodeline (not shown). The storage capacitor Cst charges the inspectionvoltage during the inspection process and then discharges the chargedvoltage. The controlling and determining circuit 3 shown in FIG. 3compares the voltage discharged from the storage capacitor Cst with apredetermined reference voltage in the inspection process, and thusdetermines a point of defect such as the short of the TFT and thestorage capacitor, or the short and the open circuit problem of thecorresponding gate line and the corresponding data line based on thecomparison results.

[0056] The device for protecting an electrostatic discharge damage(hereinafter referred to as “ESD protection device”) bypasses the staticelectricity caused during the fabricating process or the normal drivingto the electrostatic damage protection line (hereinafter referred to as“ESD protection line”) and thus protects the TFT array of an effectivedisplay from the static electricity. A ground voltage GND or a commonvoltage Vcom is supplied to the ESD protection line 404.

[0057] Further, the TFT array substrate according to the presentinvention includes first to third inspection lines 401, 402 and 405formed at an outer edge portion of the TFT array of the effectivedisplay, first and third inspection TFTs T1 and T3 having their gateterminals connected to the first inspection line 401, second TFTs T2connected between the second inspection line 402 and the gate lines GL1to GLn of the TFT array, capacitors C1 each connected between the firstand the second TFTs T1 and T2, fourth TFTs T4 connected between thethird inspection line 405 and the data lines DL1 to DLm of the TFTarray, and capacitors C2 each connected between the third and fourthTFTs T3 and T4.

[0058] The first inspection line 401 receives from, e.g., the voltagesource 7 a gate-off voltage (Vg-off) lower than the threshold voltage ofthe first and the third TFTs T1 and T3 and supplies it to the TFTs T1and T3 in the inspection process, while upon the normal driving, it isprovided with no voltage.

[0059] The second inspection line 402 receives from, e.g., the voltagesource 7 a gate-on voltage (Vg-on) higher than the threshold voltage ofthe second and the fourth TFTs T2 and T4 and supplies it to the TFTs T1,T2, and T3 in the inspection process, while upon the normal driving, itis provided with no voltage.

[0060] The third inspection line 405 receives from, e.g., the voltagesource 7 the inspection voltage Vds and supplies it to the sources ofthe fourth TFTs T4 in the inspection process. It also receives the readvoltage Vcst from the data lines DL1 to DLm. The third inspection line405 is provided with no voltage upon the normal driving.

[0061] For each first TFT T1, the gate electrode of the first TFT T1 isconnected to the first inspection line 401 and the source electrode ofthe first TFT T1 is connected to the second inspection line 402. Thedrain electrode of the first TFT T1 is connected to the capacitor C1.The first TFT T1 is turned on by a photo current generated due to theexposure to the light 1 a from the light source 1 in the inspectionprocess and thereby supplies a gate-on voltage (Vg-on) on the secondinspection line 402 to the capacitor C1.

[0062] For each second TFT T2, the gate electrode of the second TFT T2is connected to the capacitor C1 and the source electrode of the secondTFT T2 is connected to the second inspection line 402. The drainelectrode of the second TFT T2 is connected to the corresponding one ofthe gate lines GL1 to GLn. The second TFT T2 is turned on in response tothe voltage of the capacitor C1 in the inspection process, and theturned-on T2 supplies the gate-on voltage (Vg-on) on the secondinspection line 402 to the corresponding one of gate lines GL1 to GLnand thus to the TFTs of the array connected to that gate line.

[0063] For each third TFT T3, the gate electrode of the third TFT T3 isconnected to the first inspection line 401 and the source electrode ofthe third TFT T3 is connected to the second inspection line 402. Thedrain electrode of the third TFT T3 is connected to the capacitor C2.The third TFT T3 is turned on by the photo current generated due to theexposure to the light from the light source 1 in the inspection process,which supplies a gate-on voltage (Vg-on) on the second inspection line402 to the capacitor C2.

[0064] For each fourth TFT T4, the gate electrode of the fourth TFT T4is connected to the capacitor C2 and the source electrode of the fourthTFT T4 is connected to the third inspection line 405. The drainelectrode of the fourth TFT T4 is connected to the corresponding one ofthe data lines DL1 to DLm. The fourth TFT T4 is turned on in response tothe voltage of the capacitor C2 in the inspection process, which in turnsupplies the inspection voltage Vds on the third inspection line 403 tothe corresponding one of the data lines DL1 to DLm. Also, it suppliesthe read voltage Vcst from the corresponding one of the data lines DL1to DLm to the third inspection line 405 for reading by the writing andreading circuit 6.

[0065] When the first and third TFTs T1 and T3 are turned on, thecapacitors C1 and C2 charge the voltage and constantly supply thecharged voltage to the gate terminal of the second and fourth TFTs T2and T4, to thereby stably maintain the gate voltage of the second andfourth TFTs T2 and T4.

[0066] The inspection process on the TFT array substrate according to anembodiment of the present invention includes a sequence of loading theTFT array substrate shown in FIG. 4 or other substrate to the inspectiondevice, writing the inspection voltage Vds to the TFT array and readingthe return signal from the TFT array in response to the inspectionvoltage. Here, the loading step may be optional if the inspection deviceis part of the TFT array substrate (which will be discussed later inmore detail). More specifically, the TFT array substrate shown in FIG. 4is loaded in the inspection device and then the writing process of theinspection voltage as shown in FIG. 5 is performed.

[0067] Referring to FIG. 5, in the writing process of the inspectionvoltage, the inspection voltage Vds (e.g., from the voltage source 7)via the reading and writing circuit 6 shown in FIG. 3 is supplied to thethird inspection line 405, and the light is radiated by the light source1 onto a semiconductor layer of the first TFT T1 and in turn onto asemiconductor layer of the third TFT T3. In this writing process, thefirst TFT T1 is turned on by the photo current generated in itssemiconductor layer and the second TFT T2 is turned on by the voltage ofthe capacitor C1. The second TFT T2, as turned on, supplies the gate-onvoltage (Vg-on) on the second inspection line 402 to the correspondingone of the gate lines GL1 to GLn. Similarly, the third TFT T3 is turnedon by the photo current generated in its semiconductor layer and thefourth TFT T4 is turned on by the voltage of the capacitor C2, so as tosupply the inspection voltage Vds on the third inspection line 405 tothe corresponding one of the data lines DL1 to DLm. Then the TFTs of theeffective display area connected to the corresponding gate line areturned on to pass the inspection voltage Vds through the TFT(s) and tocharge the inspection voltage Vds to the corresponding storage capacitorCst. That is, the storage capacitor Cst charges electric chargessupplied through a current path i via the third inspection line 405, thecorresponding one of the data lines DL1 to DLm and the TFT in the TFTarray in the writing process of the inspection voltage.

[0068] In one embodiment, the light source 1 sequentially radiates thelight 1 a to the first and third TFTs T1 and T3 by moving with aconstant speed or moving of the stage for supporting the TFT arraysubstrate, or simultaneously radiates the light 1 a to all the first andthird TFTs T1 and T3. During the sequential radiating, all the firstTFTs T1 can be sequentially radiated and, at the same time or before orafter, all the third TFTs T3 can be sequentially radiated. In thealternative, the first and second TFTs T1 and T3 can be selectivelyradiated if a particular area (e.g., a particular TFT or Cst) on the TFTarray needs to be inspected. Other variations are possible.

[0069] After the writing process of the inspection voltage, the readingprocess of the read voltage is performed, as shown in FIG. 6. Referringto FIG. 6, in the reading process of the read voltage, no voltage isapplied from an external to the third inspection line 405 and the lightsource 1 radiates the light 1 a to the semiconductor layer of the firstTFT T1 and to the semiconductor layer of the third TFT T3. In thereading process, the first TFT T1 is turned on by the photo currentgenerated in its semiconductor layer and the connected second TFT T2 isturned on by the voltage of the capacitor C1 to supply the gate-onvoltage (Vg-on) on the second inspection line 402 to the correspondingone of the gate lines DGL and GL1 to GLn. Similarly, the third TFT T3 isturned on by the photo current generated in its semiconductor layer andthe connected fourth TFT T4 is turned on by the voltage of the capacitorC2 to form the current path between the corresponding one of the datalines DL1 to DLm and the third inspection line 405. Consequently, theTFTs of the effective display connected to the corresponding gate lineare turned on to form the current path between the storage capacitor Cstand the corresponding data lines. Then the voltage Vcst of the storagecapacitor Cst (charged with the inspection voltage) is discharged alongthe current path including the corresponding TFT, the corresponding dataline and the third inspection line 405, which will then be supplied tothe writing and reading circuit 6 shown in FIG. 3.

[0070] In one embodiment, the order or manner in which the first andthird TFT(s) T1 and T3 are radiated during the reading process of theinspection procedure can be the same as or reverse of the order ormanner in which the first and third TFT(s) T1 and T3 are radiated in thewriting process of the inspection voltage. In another embodiment, thefirst and third TFT(s) T1 and T3 can be radiated selectively accordingto an order in which particular areas of the TFT array are desired to beinspected.

[0071] The writing and reading circuit 6 amplifies the read voltage Vcstsupplied from the TFT array, removes a noise therein and supplies theprocessed read voltage Vcst to the controlling and determining circuit3. The controlling and determining circuit 3 compares the read voltageVcst with a predetermined reference data voltage to determine thepresence of a defect in the storage capacitor of the TFT array and inthe TFT and the presence of short and/or open circuit defectiveness inthe data lines DL1 to DLm and gate lines GL1 to GLn in accordance withthe comparison results. The precise location of the defect can bequickly identified by examining which one of the first TFTs T1 and whichone of the third TFTs T3 have been radiated to read the chargeinspection voltage. This is because each of the first TFTs T1 isassigned to one of the gate lines, and each of the third TFTs T3 isassigned to one of the data lines.

[0072] The controlling and determining circuit 3 supplies the data ofthe read voltage Vcst and/or the comparison result to the display device4 or other indication device to allow an inspection operator or userrecognize the defect in real time.

[0073] In one embodiment, the inspection device is a removable part ofthe TFT array substrate. In this case, the edge of the TFT arraysubstrate is cut off along a cutting line 400 of FIG. 4 upon thescribing process. Accordingly, the first to the fourth TFTs T1 to T4,the capacitors C1 and C2 and the first to the third inspection lines401, 402 and 405 are removed from the TFT array substrate after theinspection is completed. Then, after forming the liquid crystals Clc bythe alignment film forming/rubbing process and the substrateassembling/liquid crystal injecting process, integrated circuits of adata driving circuit 702 and a scan driving circuit 701 are mounted onthe TFT array substrate as shown in FIG. 7.

[0074] The data driving circuit 702 supplies video data to the datalines DL1 to DLm under control of the timing controller (not shown). Thescan driving circuit 701 sequentially supplies a scan pulse to the gatelines GL1 to GLn in response to the gate start pulse from the timingcontroller to select the lines to which the video data voltage issupplied. This process is known.

[0075] In other variations, upon the scribing process, the first to thefourth TFTs T1 to T4, the capacitors C1 and C2 and the first and thethird inspection lines 401, 402 and 405 may be remained on the TFT arraysubstrate without being removed from the TFT array substrate. In thiscase, as shown in FIG. 8, it is preferred to form a light cut-off layer803 covering or overlapping the inspection device including the TFTs T1to T4 and the inspection lines, so that the TFTs T1 to T4 on the edge ofthe TFT array substrate do not cause a false operation. Then, afterforming the liquid crystal cells Clc by the alignment filmforming/rubbing process and substrate assembling/liquid crystalinjecting process, the integrated circuits of a data driving circuit 802and a scan driving circuit 801 are mounted on the TFT array substrate.

[0076] The processing steps and computer programs of the presentinvention are implementable using existing computer programminglanguage. Such computer program(s) may be stored in memories such asRAM, ROM, PROM, etc. associated with computers. Alternatively, suchcomputer program(s) may be stored in a different storage medium such asa magnetic disc, optical disc, magnet-optical disc, etc. Such computerprogram(s) may also take the form of a signal propagating across theInternet, extranet, intranet or other network and arriving at thedestination device for storage and implementation. The computer programsare readable using a known computer or computer-based device.

[0077] As described above, the method and apparatus for inspecting theliquid crystal display device provide the inspection lines and the TFTsat an edge area of the TFT array substrate, radiate the light to theTFTs in order to charge the inspection voltage to the storage capacitorof the TFT array substrate, and read the voltage of the storagecapacitor of the TFT array substrate to find the defect in the TFT andthe storage capacitor formed on the TFT array substrate and the shortand the open circuit problems of the signal wirings. As a result, themethod and apparatus for inspecting the liquid crystal display deviceaccording to the present invention do not need a separate jig and candetect the defect location precisely and rapidly.

[0078] Although the present invention has been explained by theembodiments shown in the drawings described above, it should beunderstood to the ordinary skilled person in the art that the inventionis not limited to the embodiments, but rather that various changes ormodifications thereof are possible without departing from the spirit ofthe invention. Accordingly, the scope of the invention shall bedetermined only by the appended claims and their equivalents.

What is claimed is:
 1. A method of inspecting a liquid crystal displaydevice using an inspection apparatus, the inspection apparatus includinga light source, at least one inspection line and at least one inspectionswitch device connected to the inspection line, the method comprising:providing a substrate, wherein the substrate includes a plurality ofsignal wirings, a plurality of drive switches, and a plurality ofcapacitors formed in an effective display area of the substrate;radiating a light generated from the light source of the inspectionapparatus onto the at least one inspection switch device and therebysupplying an inspection voltage from the at least one inspection line toa corresponding one of the drive switches through the signal wirings, soas to charge a corresponding one of the capacitors; and determining ifthere is a defect in the effective display area of the substrate byreading the charged voltage of the corresponding one of the capacitors.2. The method according to claim 1, wherein the determining stepincludes: comparing the charged voltage of the corresponding one of thecapacitors with a predetermined reference voltage.
 3. The methodaccording to claim 1, wherein the signal wirings include a plurality ofgate lines, the at least one inspection switch device includes first andsecond inspection switch devices, and the at least one inspection lineincludes first and second inspection lines, and wherein the radiatingstep includes: radiating a light from the light source onto the firstinspection switch device to turn on the first inspection switch device;and turning on the second inspection switch device under control of thefirst inspection switch device and thereby supplying a first inspectingvoltage from the first inspection line to a corresponding one of thegate lines, so as to turn on the corresponding one of the drivingswitches.
 4. The method according to claim 3, wherein the signal wiringsfurther include a plurality of data lines, and the at least oneinspection switch device further includes third and fourth inspectionswitch devices, and wherein the radiating step further includes:radiating a light onto the third inspection switch device to turn on thethird inspection switch device; and turning on the fourth inspectionswitch device under control of the third inspection switch device andthereby supplying a second inspection voltage from the second inspectionline to a corresponding one of the data lines, so as to charge thecorresponding one of the capacitors.
 5. The method according to 4,wherein the determining step includes: radiating a light onto the firstand third inspection switch devices; and reading the charged voltage ofthe corresponding one of the capacitors, to thereby determine if thereis a defect in at least one of the signal wirings, the driving switchdevices and the capacitors.
 6. The method according to claim 1, whereinthe inspection apparatus is formed on the substrate as part of thesubstrate.
 7. The method according to claim 1, further comprising:informing a user of the determination result in real time.
 8. A methodof inspecting a substrate device, the substrate device including signalwirings, drive switches and capacitors formed in a main area of thesubstrate device, and an inspection line and an inspection switch formedat an exterior of the main area, the drive switches being coupled to thecapacitors, the inspection switch being coupled to the inspection line,the method comprising: supplying an inspection voltage to the inspectionline of the substrate device; charging one of the capacitors with theinspection voltage through the signal wirings; and determining if thereis a defect in the substrate device by reading the charged voltage ofthe capacitor.
 9. The method according to claim 8, wherein thedetermining step includes: comparing the charged voltage of thecapacitor with a predetermined reference voltage; and determiningwhether or not there is a defect in one of the signal wirings, acorresponding one of the drive switches, or the charged capacitor basedon the comparison result.
 10. The method according to claim 8, whereinthe charging step includes: turning on a corresponding one of the driveswitches; and radiating a light onto the inspection switch to turn onthe inspection switch, so as to charge the one of the capacitors. 11.The method according to claim 8, further comprising: severing, from thesubstrate device, the inspection line and the inspection switch formedat the exterior of the main area of the substrate device after aninspection of the main area is completed.
 12. The method according toclaim 8, further comprising: covering, with a light cut-off layer, theinspection line and the inspection switch formed at the exterior of themain area of the substrate device after an inspection of the main areais completed.
 13. A method of inspecting a display part of a liquidcrystal display device, the method comprising: providing an inspectionapparatus as a removable portion of the liquid crystal display device;inspecting the display part of the liquid crystal display device usingthe inspection apparatus; removing the inspection apparatus from theliquid crystal display device after the inspection is completed; andattaching driving circuits to the liquid crystal display device havingthe inspection apparatus removed therefrom.
 14. The method according toclaim 13, wherein in the attaching step, the driving circuits areattached to areas of the liquid display device where the inspectionapparatus was previously located.
 15. A method of inspecting a displaypart of a liquid crystal display device, the method comprising:providing an inspection apparatus as an integral part of the liquidcrystal display device; inspecting the display part of the liquidcrystal display device using the inspection apparatus; covering theinspection apparatus with a light cut-off layer after the inspection iscompleted; and attaching driving circuits to the liquid crystal displaydevice after the inspection is completed.
 16. The method according toclaim 15, wherein in the attaching step, the driving circuits areattached to certain sides of the liquid crystal display device otherthan those sides of the liquid crystal display device where the coveredinspection apparatus is located.
 17. An inspection apparatus for aliquid crystal display device, the liquid crystal device including aplurality of signal wirings, a plurality of driving switch devices and aplurality of capacitors formed on a substrate and formed in an effectivedisplay area of the liquid crystal display device, the apparatuscomprising: at least one inspection line formed at an exterior of theeffective display area of the liquid crystal display device; at leastone inspection switch device connected to the at least one inspectionline and formed at an exterior of the effective display area; a lightsource to radiate light onto the at least one inspection switch device,so as to turn on the at least one inspection switch device and to chargean inspection voltage from the at least one inspection line onto one ofthe capacitors; and a control part to read the charged voltage of theone of the capacitors and thereby determine if there is a defect in theeffective display area of the liquid crystal display device.
 18. Theapparatus according to claim 17, wherein the at least one inspectionswitch device includes: a first transistor to be turned on in responseto the light from the light source; and a second transistor to be turnedon in response to an output voltage of the first transistor.
 19. Theapparatus according to claim 18, wherein the at least one inspectionline includes: a first inspection line to which a gate-off voltage lowerthan a threshold voltage of the first transistor is supplied and a gateterminal of the first transistor is connected; and a second inspectionline to which a gate-on voltage higher than a threshold voltage of thesecond transistor is supplied and a source terminal of each of the firstand second transistors is connected.
 20. The apparatus according toclaim 19, wherein the signal wirings include: a gate line connected tothe second transistor; and a plurality of data lines crossing with thegate line.
 21. The apparatus according to claim 20, wherein a drainterminal of the first transistor is connected to a gate terminal of thesecond transistor and a drain terminal of the second transistor isconnected to the gate line.
 22. The apparatus according to claim 18,further comprising: a capacitor connected between a drain terminal ofthe first transistor and a gate terminal of the second transistor tostabilize a gate voltage of the second transistor.
 23. The apparatusaccording to claim 17, wherein the at least one inspection switch deviceincludes: a third transistor to be turned on in response to the lightfrom the light source; and a fourth transistor to be turned on inresponse to an output voltage of the third transistor.
 24. The apparatusaccording to claim 23, wherein the at least one inspection lineincludes: a first inspection line to which a gate-off voltage lower thana threshold voltage of the third transistor is supplied and a gateterminal of the third transistor is connected; a second inspection lineto which a gate-on voltage higher than a threshold voltage of the fourthtransistor is supplied and a source terminal of the third transistor isconnected; and a third inspection line through which the charged voltageof the one of the capacitors is transmitted after the inspection voltageis applied and to which a source terminal of the fourth transistor isconnected.
 25. The apparatus according to claim 24, wherein the signalwirings include: a data line connected to the forth transistor; and aplurality of gate lines crossing the data line.
 26. The apparatusaccording to claim 25, wherein a drain terminal of the third transistoris connected to a gate terminal of the fourth transistor and a drainterminal of the fourth transistor is connected to the data line.
 27. Theapparatus according to claim 23, further comprising: a capacitorconnected between a drain terminal of the third transistor and a gateterminal of the fourth transistor to stabilize a gate voltage of thefourth transistor.
 28. The apparatus according to claim 17, furthercomprising: a light cutting-off layer to shield the at least oneinspection switch device and the at least one inspection line fromlight.
 29. An apparatus for inspecting a substrate of a liquid crystaldisplay device, the substrate including a plurality of signal wirings, aplurality of drive switches and a plurality of capacitors formed in aneffective display area of the substrate, the apparatus comprising: alight source to radiate light; at least one inspection line formed at anexterior of the effective display area of the substrate; at least oneinspection switch device connected to the at least one inspection lineand formed at an exterior of the effective display area of thesubstrate, wherein the at least one inspection switch device is radiatedwith the light from the light source so as to be turned on to supply aninspection voltage of the at least one inspection line to acorresponding one of the drive switches, whereby a corresponding one ofthe capacitors is charged through the signal wirings; and a determiningpart to determine if there is a defect in the effective display area ofthe substrate by reading the charged voltage of the corresponding one ofthe capacitors.
 30. The apparatus according to claim 29, wherein thedetermining part compares the charged voltage of the corresponding oneof the capacitors with a predetermined reference voltage to make thedetermination.
 31. The apparatus according to claim 29, wherein thewiring signals include a plurality of gate lines, the at least oneinspection line includes first and second inspection lines, and the atleast one inspection switch device includes first and second inspectionswitch devices.
 32. The apparatus according to claim 31, wherein thefirst inspection switch device is turned on in response to the lightfrom the light source, the second inspection switch device is turned onunder control of the first inspection switch device to supply a firstinspecting voltage from the first inspection line to a corresponding oneof the gate lines, which turns on the corresponding one of the driveswitches.
 33. The apparatus according to claim 32, wherein the wiringsignals further include a plurality of data lines and the at least oneinspection switch device further includes third and fourth inspectionswitch devices, and wherein a light from the light source is radiatedonto the third inspection switch device to control the third inspectionswitch device, the fourth inspection switch device is turned on undercontrol of the third inspection switch device to supply a secondinspection voltage from the second inspection line to a correspondingone of the data lines so as to charge the corresponding one of thecapacitors.
 34. The apparatus according to 33, wherein a light from thelight source is radiated onto the first and third inspection switchdevices, and the determining part determines if there is a defect in atleast one of the signal wirings, the drive switches and the capacitorsbased on the charged voltage of the one of the capacitors.
 35. Theapparatus according to claim 29, wherein the apparatus is part of thesubstrate.
 36. The apparatus according to claim 29, further comprising:means for informing a user of the determination result in real time. 37.A display part of a liquid crystal display device, comprising: asubstrate; a display circuit on the substrate for performing a displayfunction of the liquid crystal display device; and an inspectionapparatus formed at an exterior of the display circuit and being aremovable portion of the liquid crystal display device, wherein afterthe display circuit is inspected for any defect using the inspectionapparatus, the inspection apparatus is removed from the liquid crystaldisplay device.
 38. The display part according to claim 37, furthercomprising: driving circuits attached to the exterior of the displaycircuit once the inspection apparatus is removed.
 39. A display part ofa liquid crystal display device, comprising: a substrate; a displaycircuit on the substrate for performing a display function of the liquidcrystal display device; an inspection apparatus formed as an integralpart of the liquid crystal display device at an exterior of the displaycircuit; and a light cut-off layer covering the inspection apparatusafter the display circuit is inspected using the inspection apparatus;and driving circuits attached to the liquid crystal display device afterthe display circuit is inspected using the inspection apparatus.
 40. Thedisplay part according to claim 39, wherein the driving circuits areattached to certain sides of the liquid crystal display device otherthan those sides of the liquid crystal display device where the coveredinspection apparatus is located.